The present invention refers to a dual voltage electrical distribution system applicable to vehicles which possess two network sectors and charges prepared to operate at two different voltage levels, for example at 42 V and at 14 V, generated by at least two batteries, one of which is at a first voltage level of, e.g. 36 V, and another at a second lower voltage level of, e.g. 12 V, there being at least one voltage converter associated with the two said network sectors.
The present invention is useful in the automotive industry.
In modern vehicles there is a tendency towards increasing electrical and electronic equipment which results in a growing consumption of electrical energy. This makes it advisable to increase the current nominal voltage of the vehicle""s electrical system by up to three times, that is, from the current 14 V DC to 42 V DC. However, due to the conveniently calculated and designed current manufacturing and installation infrastructures of electrical systems which already exist in the automotive industry, a sudden transition from one voltage to another is made very difficult.
A solution has been proposed in order to avoid said sudden transition, which consists of implementing an electrical and electronic distribution system architecture for the vehicle using networks operating at two different voltage levels, which has been called xe2x80x9cdual voltage systemxe2x80x9d. Thus, some components will continue to work at 14 V, as until now, so that it will not be necessary to introduce changes in their electrical control and distribution networks, while other components will come to work at 42 V, with a more appropriate output and/or optimisation of their performance.
Said dual voltage system may be basically achieved in two ways: either with a single 42 V battery and a unidirectional DC/DC voltage converter from 42 to 14 V; or with two 14 and 42 V batteries respectively, and a bidirectional DC/DC voltage converter from 14 to 42 V or vice versa.
The converter is a key piece of the new system in any of the solutions.
Patent WO 97/28366 is an example of the utility of having a dual voltage system in automotive vehicles, describing an ignition system for internal combustion engines which uses a dual voltage electrical supply, with a higher voltage to produce a high-intensity electric arc and a lower voltage to cause ionisation. A signal controller analyses the ionisation signal to determine a series of parameters concerning the correct operation of the ignition.
Patent WO 95/13470 describes another ignition system for internal combustion engines supplied by dual voltage supplied by a single supply source and subsequently dualised by a DC/DC voltage converter.
Patent EP-A-0892486 describes a unidirectional converter device to supply dual voltage from a single supply source.
The introduction of the new architecture of the dual voltage system in automotive vehicles carries with it an increase in the complexity of electrical networks. The system includes, as stated hereinbefore, one or two accumulators or batteries, a converter and one or more distribution boxes in which electronic signal and power control means are centralised, including a microprocessor and electrical protection means. The vehicle also comprises an electric generator, usually an alternator, which supplies current to the accumulator or accumulators by means of a rectifier, and which also directly supplies most of the components when the vehicle is running.
Increasing the voltage (Volts.) threefold (42 V) involves the reduction of current (A) for the same amount of power. Fewer amperes mean smaller cable cross-section for supplying current, with consequently less weight and lower consumption.
References to the subject and objects of this invention are also found in different publications, among which the following may be mentioned: J. G. Kassakian xe2x80x9cChallenges of the new 42 V architecture and progress on its international acceptancexe2x80x9d VDI 98 Baden-Baden; Intersociety Energy Conversion Engineering Conference (IECEC) xe2x80x9cMultiple Voltage Electrical Power Distribution System for Automotive Applicationsxe2x80x9d 31st. Washington 96; xe2x80x9cDraft specification for 42 V battery in a 2-voltage vehicle electrical system for BMW and Daimler-Benz SICANxe2x80x9d 29.6.98; MIT Auto-Consortium-42V Net Research Unit #1 xe2x80x9cDC/DC converters for Dual Voltage Electrical Systemsxe2x80x9d.
Kazimierczuk M K et al. xe2x80x9cTopologies of Bidirectional PWM DCxe2x80x94DC power convertersxe2x80x9d PROCEEDINGS OF THE NATIONAL AEROSPACE AND ELECTRONICS CONFERENCE. (NAECON 1993), US, NEW YORK, IEEE, VOL 1, pages 435441, describes a power system of an aircraft for normal and emergency operation (see FIG. 1) as well as several block diagrams and topologies of bidirectional converters, in particular FIG. 3 equivalent to the topology of FIG. 3 of the drawings of this invention, which are detailed in the preamble of claim 1 of the invention.
In accordance with the invention, the dual voltage electrical distribution system will to be implemented using a bi-directional voltage converter, with its input and output stages galvanically insulated, and including in each of said stages a switching device, whose bi-directional converter has said batteries at a first voltage level and at a second voltage level connected to said inputs and outputs, so that said bi-directional converter circuit provides two energy transfer modes which constitute a first mode of voltage reduction and a second mode of voltage raising, having chosen the passive components, that is the magnetic components and capacitances of said stages to provide an identical transitory behaviour in both modes when either a disturbance in the charge or in the input voltage enters into the regulation system.
More specifically, the proposed bi-directional converter is a galvanically insulated DC version of a converter circuit with the Cuk topology, symmetrical with respect to the area of insulation, in which said batteries are connected to its input and output at a first voltage level and at a second voltage level respectively, with a capacitance in parallel with each of said voltage sources, in addition to the storage capacitance typical of the topology, in series with the inductances of the input and output circuit, said switching device being arranged in the input and output stages of the converter, on each side of said galvanic insulation.
The main differences between the basic unidirectional converter circuit and the proposed converter are:
a) bi-directional power flow;
b) no change in output voltage polarity;
c) simplification of the converter control design.
The invention will be better understood from the following description given in connection with the attached drawings.
Until now, the converter has been situated in some part of the electrical networks separated from the distribution box or boxes. However, this arrangement has several drawbacks, such as: an increase in the connection cabling which, on the one hand, involves a greater voltage drop and, on the other, affects the manufacturing cost, the vehicle""s weight and, consequently, fuel consumption; also, a greater occupation of the volume inside the already scarce space of the engine compartment; an increase in the fixing points of components to the vehicle with greater complexity of assembly; an increase in the number of electrical components subjected to vibration, which reduces the system""s reliability; a redundancy of systems, for example, a microprocessor for the converter and a microprocessor for the distribution box; greater difficulty for thermal dissipation of components arranged in separate boxes; greater difficulty in achieving electromagnetic compatibility due to the incorporation of cables which produce high frequency emissions which cause interference in the components of the distribution box.
The invention also proposes to incorporate said bi-directional voltage converter in an electrical distribution box of the vehicle, together with centralised electronic signal and power control means, including a microprocessor and electrical protection means.
The invention will be better understood from the following description of embodiments, with reference to illustrative drawings.